Differential Units; Differential Units (87-1) (87-2) - GE Multilin MIB Instruction Manual

High impedance bus differential relay

Table of Contents

2 PRODUCT DESCRIPTION

2.4 DIFFERENTIAL UNITS

2.4DIFFERENTIAL UNITS

MIB provides 2 Differential Units, 87 1 and 87 2. Each one can be enable/disable and set independently.

These elements consist on overcurrent detectors that measure the current flowing in the High-impedance differential

circuits. The pick up value can be set between 5 mA and 400 mA, and the time delay from 0 to 600 seconds.

For a Bus-bar differential application, these elements will receive the differential currents corresponding to phase A, B and

C. The elements will measure the three differential currents, and operate if any of them surpass the pickup setting during

the specified time delay.

For a one-grounded-winding transformer RGF application, these elements will receive the differential current corresponding

to the ground connection in one winding and operate if it surpass the pickup setting during the specified time delay.

For a two-grounded-windings transformer RGF application, this element will receive the differential currents corresponding

to the ground connection in each of the two windings and operate if any of the two ground differential currents surpass the

pickup setting during the specified time delay.

GEK-106426B

MIB High Impedance Bus Differntial Relay

2-7

Table of Contents

90.017.102